The invention relates to self-propelled implements, and, more particularly, to self-propelled lawn mowers. Still more particularly, the invention relates to operator actuated means for controlling the speed of self-propelled lawn mowers.
It is known in the art to provide self-propelled implements, and particularly self-propelled lawm mowers, which move forward when the operator handle is lifted or pushed forward. Examples of such implements are disclosed in some of the patents listed below.
Most known self-propelled lawn mowers operate at two speeds: zero speed and full speed. The operator is effectively unable to operate the lawn mower at intermediate speeds. Also, such lawn mowers are typically rear wheel drive and therefore tend to "wheelstand" when the drive system is engaged. This is undersirable because it impairs control of the lawn mower and results in uneven mowing. Wehner U.S. Pat. No. 2,860,473 discloses a lawn mower with a three-speed (zero, low and high speeds) transmission which operates in response to actuation of a shift lever mounted on the lawn mower handle.
Parikh U.S. Pat. No. 4,404,864 and the references cited therein disclose variable speed driving mechanisms including a driven wheel and a driving wheel, with the driving wheel being rotatable in a plane normal to the plane of the driven wheel, and with the speed of rotation of the driven wheel being variable by varying the distance between the driving wheel and the axis of rotation of the driven wheel.
Attention is directed to the following U.S. Patents:
______________________________________ Shaw 2,947,132 Jones 4,117,652 Oct. 3, 1978 Wehner 2,860,473 Nov. 18, 1958 Irgens 2,138,239 Nov. 29, 1938 Roberton 2,285,230 June 2, 1942 Rodesci 2,468,839 May 3, 1949 Melling 2,453,999 Nov. 16, 1948 Walstrom 2,514,917 July 11, 1950 Smith, et al. 2,564,586 Aug. 14, 1951 Herman 2,585,315 Feb. 12, 1952 Cutlan, et al. 2,623,603 Dec. 30, 1952 Frazier 2,824,415 Feb. 25, 1958 Kortum 3,396,809 Aug. 13, 1968 Prien, Jr. 3,613,814 Oct. 19, 1971 Sheler 3,823,791 July 16, 1974 Block 4,108,268 Aug. 22, 1978 Miyazawa, et al. 4,212,141 July 15, 1980 Takeuchi, et al. 4,213,288 July 22, 1980 Wick 4,493,180 Jan. 15, 1985 Parikh 4,404,864 Sept. 20, 1984 Van Der Meulen 4,265,133 May 5, 1981 Enters 3,678,770 July 25, 1972 Mollen 3,580,351 May 25, 1971 Hunt 1,143,048 June , 1915 Swift 974,308 Nov. 1, 1910 ______________________________________